1. Field of the Invention
The invention relates generally to the field of actuators used in subsurface wellbores. More particularly, the invention relates to actuators using a wound fiber composite layer as an active element.
2. Background Art
Various types of actuators are used in wellbores drilled through subsurface formations. The actuators are used, for example to operate valves that control the flow of fluids into and out of the well. Actuators known in the art include, for example, electrically operated solenoids, motor and gear set combinations and hydraulic actuators (a piston disposed in a cylinder and controllably pressurized with hydraulic fluid or compressed gas). In certain circumstances it is desirable to control very large forces, such as pressure of fluid entering the wellbore from a subsurface formation, while minimizing the amount of control force needed to effect control.
Fiber composite materials are known in the art for a number of purposes, including shafts and rods, as well as fluid carrying conduits. Examples of the latter are disclosed, for example, in U.S. Pat. No. 6,620,475 issued to Reynolds, Jr. et al. Generally, a fiber composite material includes fiber arranged in a selected geometric pattern embedded in a “matrix” which may be plastic, cement, elastomer or other material that bonds to the fiber and provides structural integrity to the composite.
U.S. Pat. No. 4,877,375 issued to Desjardins discloses a flexible shaft made out of flexible matrix composites for use in helicopter applications. A rotor system disclosed in the '375 patent includes a structurally flexible rotor shaft for transmitting rotor torque and other rotor loads to a rotor hub. The rotor hub is configured to have rotor blades mounted thereon and is mounted by an elastomeric spherical bearing whose center is located at the rotor center. A flexible shaft made from fiber reinforced resin matrix material is connected to the rotor shaft at a connection located below the bearing center and extends vertically from that location through the bearing to a position located above the bearing center. There, the shaft is connected to a connecting member fixed to the upper surface of the rotor hub. The flexible shaft is structurally stiff with respect to the mode in which it transmits rotor torque compared to the rotor torque stiffness of the other components. However, the bending stiffness and axial stiffness of the flexible shaft is substantially less compared to the mode in which rotor moments and forces are transmitted from the other components to the rotor shaft.
U.S. Pat. No. 6,508,806 discloses guiding or angiography catheters, having a catheter shaft formed of a multi-layer wire reinforced wall construction consisting of one layer of wire wrapped in a substantially circumferential manner and another layer of wire laid at an angle of about 20 degrees to about 75 degrees with respect to the longitudinal axis of the tubular shaft.
European Patent No. 0 213 816 discloses a composite member and a method for making the composite member where such members may be made of flexible matrix material and stiff filamentary material wound at optimized angles to a longitudinal axis so that a maximum torsional to bending stiffness ratio is provided, while producing within the structural member the minimum possible bending stresses. The member is thereby able to carry larger loads. The disclosed structure provides members that are flexible in bending and in axial modes but stiff in torsional modes and produce low bending stresses. Such members are particularly suited for applications where torsional loads are to be transmitted and misalignment has to be accommodated.
It is also known in the art to use fiber composite materials as actuators. See, for example, Shan, Y., and Bakis, C. E., Flexible Matrix Composite Actuators, 20th Annual Technical Conference of American Society for Composites (ASC), Sep. 7-9, 2005, Philadelphia, Pa., which discloses flexible matrix composite actuators.
There continues to be a need for improved actuators for wellbore applications. It is desirable to apply the principles of flexible matrix composite actuators to making actuators for wellbore control applications.